Seta-triazolo-(3,4-a)isoquinolines in reducing inflammation

ABSTRACT

NOVEL S-TRIAZOLO-(3,4-A)-ISOQUINOLINE COMPOUNDS ARE PREPARED BY METHODS ANOLOGOUS TO KNOWN METHODS AND EXHIBIT ANTI-FLAMMATORY ACTIVITY.

United States Patent Oflice Patented July 9, 1974 ABSTRACT OF THE DISCLOSURE Novel s-triazolo-[3,4-a]-isoquinoline compounds are prepared by methods analogous to known methods and exhibit anti-inflammatory activity.

1 Claim This is a division of application Ser. No. 166,626, filed July 27, 1971 now abandoned.

BACKGROUND OF THE INVENTION The present invention relates to the pharmaceutical field, and more particularly to methods and pharmaceutical compositions for treating mammals utilizing as active agents certain novel organic heterocyclic compounds from the class known as s-triazolo-[3,4-a1-isoquinolines.

The preparation of various s-triazolo-[3,4-a]-isoquinolines is disclosed by (1) S. Naqui et al., Indian J. Chem., 3, 1624 (1965); (2) G. S. Sidhu et al., Jour. Heterocyclic Chem, 3, 158-164 (1967); (4) H. K. Reimlinger et al., French Pat. 1,573,135 (1969) and (5) H. K. Reimlinger et al., Chem. Ber. 103, 1960-4981 (1970).

No pharmaceutical compositions or utility are disclosed in references (1), (2), (4) and (5) cited above. Francis (3) discloses that unsubstituted s-triazolo-[3,4-a]-isoquinoline and its 3-lower alkyl derivatives are coronary vasodilators.

The invention is particularly concerned with certain novel compounds useful in the treatment of inflammatory disorders, among which are the conditions known as arthritis.

The term arthritis is applied to a group of related disorders of the joints which are characterized by pain, inflammation and stiffness. Certain types of arthritis are due to specific infectious agents, but no specific cause is known for the most common type, known as rheumatoid arthritis. While this is primarily an inflammatory disease of the joints, it is sometimes accompanied by pedal edema, that it, an accumulation of fluid in the tissues of the foot. Treatment of this disease involves the administration of agents which have been found effective in reducing the pain and the inflammation. Such-agents have come to be generally known as anti-inflammatory agents.

Chemical compounds having structures of varying complexity, from the structurally simple aspirin to relatively complex steroid compounds, are known to be useful antiinflammatory agents in the treatment of arthritic and related disorders in man and other mammals. Among such recognized anti-infiammatory agents, in addition to aspirin, are the following, to which reference may be conveniently made in the Merck Index, 8th Ed., Merck & Co., Rahway, NJ. (1968): dexamethasone (p. 334), hydrocortisone (p. 542) indomethacin (p. 566), mefenamic acid (p. 648) and phenylbutazone (p. 815). However, s-triazolo-[3,4-a]-isoquinoline compounds have not heretofore been recognized as having anti-inflammatory activity.

SUMMARY OF THE INVENTION Among the several objects of the invention may be noted the provision of certain novel s-triaZ01o-[3,4-ai]-is0- quinolines; the provision of such compounds which exhibit anti-inflammatory activity; and the provision of pharmaceutical compositions and methods for combatting an inflammatory reaction in a susceptible mammal, which compositions and methods utilize the novel s-triazol0-[3,4-a]- isoquinolines as active agents. Other objects will be in part apparent and in part pointed out hereinafter.

The present invention is thus directed to novel s-triazolo-[3,4-a]-isoquinoline compounds from the group hereinafter specifically set forth. The invention is also directed to a method of combatting an inflammatory reaction in a susceptible mammal by administering to said mammal an effective amount of such an s-triazolo-[3,4-a]- isoquinoline compound and to pharmaceutical compositions comprising such a compound and a pharmaceutical carrier.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the present invention, it has now been found that certain novel s-triazolo-[3,4-a1-isoquinoline compounds exhibit activity as anti-inflammatory agents. The type and degree of activity observed with striazolo-[3,4-a1-isoquinoline compounds is selective in nature and the presence or absence of such activity, and its degree when present, appears to be quite sensitive to the position and type of substitution on the basic s-triazolo- 3,4-a] -isoquinoline structure.

The novel s-triazolo-[3,4-aJ-isoquinoline compounds of the invention which have been found to possess anti-inflammatory activity are:

3-chlorodifiuoromethyl-s-triazolo- 3,4-a] -isoquinoline 3 -trifluoromethyl-5, -dihydro-s-triazolo- [3,4-a] -isoquinoline and the pharmaceutically acceptable, nontoxic acid addition salts thereof. Such addition salts may be derived from hydrochloric acid, hydrobromic acid, phosphoric acid, methanesulfonic acid and the like.

In addition to anti-inflammatory activity, the compound 3 trifluoromethyl-S,6-s-triazolo-[3,4-a]-isoquinoline advantageously exhibits anti-secretory activity rather than the ulcerogenic properties exhibited by certain prior art anti-inflammatory agents, such as the cortical steroids.

As illustrated by the working examples hereinafter, the novel compounds of the invention may be prepared by methods analogous to those disclosed in H. K. Reimlinger et al. French Pat. 1,573,135 (1969). Thus, 3-chlorodifluoromethyl-s-triazolo-[3,4-a]-isoquinoline is prepared by reaction of 1-hydrazinoisoquinoline and chlorodifluoroacetic acid as the acidic reagent. 3-Trifiuoromethyl-5,6- dihydro-s-triazolo-[3,4-a]-isoquinoline is prepared by catalytic hydrogenation of 3-trifluoromethyl-s-triazolo-[3,4-a]- isoquinoline.

In further accordance with the invention, pharmaceutical compositions and methods useful for combatting inflammatory reactions in susceptible mammals are provided, the compositions comprising an aforementioned s-triazolo-[3,4-a]-isoquinoline compound and a pharmaceutical carrier which may be either liquid or solid material. These compositions may be administered orally or parenterally in the usual pharmaceutical forms including capsules, tablets, solutions, suspensions and the like. For example, the s-triazolo[3,4-a]-isoquinoline compounds may be formulated with carriers such as magnesium stearate and lactose and filled into gelatin capsules. Examples of other solid pharmaceutical carriers, such as fillers, binders and lubricants, include dibasic calcium phosphate, calcium sulfate dihydrate, microcrystalline cellulose, cal cium carbonate and talc. The pharmaceutical compositions of the invention may also be in the form of sterile parenteral solutions with the s-triazolo-[3,4-a]-isoquinoline compound dissolved in a sterile parenteral solvent such as polyethylene glycol, propylene glycol, Water or mixtures of solvents or the compositions may be in the form of suspensions.

Where the s-triazolo-[3,4-a]-isoquinoline compound is water-insoluble, it is preferred that the compound be formulated into the pharmaceutical compositions of the invention in a micronized form, as by milling the compound by conventional methods. More particularly, it is preferred that the compound be micronized to a particle size of approximately 1-10 microns.

The following examples illustrate the invention.

In each of Examples 1 and 2, the indicated structure was confirmed by infrared spectroscopy.

EXAMPLE 1 Preparation of 3-Chlorodifiuoromethyl-s-triazolo- [3,4-a] -isoquinoline l 1 ON CClFzCOOH N \J-CIMCI l-Hydrazinoisoquinoline (8 g.) and chlorodifluoroacetic acid (60 ml.) were heated at reflux. Excess acid was removed in vacuo and the residue was suspended in water and treated with sodium bicarbonate. The solid was filtered and recrystallized from cyclohexane to provide the product in a yield of 90%; mp. 119-120 C.

Calculated for C H ClF N C, 52.09; H, 2.38; N, 16.57. Found: C, 52.20; H, 2.69; N, 16.33.

EXAMPLE 2 Preparation of 3-Trifluoromethyl-5,6-dihydro-striazolo-'[ 3,4-a] -isoquinoline 3-Trifiuoromethyl-s-triazolo-[3,4-a]-isoquinoline (5 g.) was dissolved in 250 ml. of 2-propanol and 5% palladium on charcoal (0.5-1 g.) was added. The hydrogenation was conducted at 90-110 C. at 50 atm. for 24-36 hours (until a bend in the hydrogenation curve was observed). The catalyst was removed by filtration and the filtrate was concentrated in vacuo. After recrystallization, the product was obtained in a yield of 50%, mp. 116 C.

Calculated for C H F N C, 55.23; H, 3.37; N, 17.57. Found: C, 55.03; H, 3.55; N, 17.21.

EXAMPLE 3 The anti-inflammatory activity of 3-trifluoromethyl-5,6- dihydro-s-triazolo-[3,4-a]-isoquinoline was determined by measuring inhibition of carrageenin-induced pedal edema in rats. The procedure used was a modification of the method of Winter at al., Proc. Soc. Exptl. Biol. Med. 111: 544 (1962). The device used for measurement of the paw volume was an adaptation of the water displacement procedure described by Adamkiewicz et al., Can. J. Biochem. Physiol. 33: 332 (1955). The compound was studied for its effectiveness in inhibiting the edema caused by the intraplantar injection of 0.05 ml. of a sterile 1.0% solution of carrageenin. Rats (male Westar, 100 to 175 grams) were employed and were fasted for approximately 18 hours prior to use.

The compound was administered as a finely divided suspension in a 0.25% methylcellulose solution. The compound was administered orally or by intraperitoneal injection one hour prior to the injection of the phlogistic substance (carrageenin) into the left hind paw of the rats. At peak swelling time (3 hours), the volume of edema was calculated by differential paw volumes. The ED value was obtained and is defined as that dose which reduced edema formation by 25% or more compared with the mean control response (parallel run) in 50% of the animals.

It was found that the ED' upon oral administration of the compound to intact rats was 23.1 mm./kg. and, upon intraperitoneal injection to intact rats, the ED- was found to be 42.75 mg./kg. It was also found that the ED upon oral administration of the compound to adrenalectomized rats was 9.9 mg./kg. Typical ED' values (oral) for known anti-inflammatory agents include aspirin224, phenylbutazone-30 and hydrocortisone acetate26.

The procedure was repeated using guinea pigs as the test animals and the E-D was found to be 5-25 mg./kg.

Inhibition of granuloma formation was determined by a modification of the method of Meier et al., Experentia 6: 469 (1950). Essentially it consisted of the subcutaneous implantation of a sterile cotton disc into intact rats with concomitant oral administration of 3-trifluoromethyl- 5,6-dihydro-s-triazolo-[3,4-a] -isoquinoline twice daily for four days. Removal of the pellets along with the granuloma formation after five days was performed and the increment in dry weight considered as the measure of granuloma formation. The ED was obtained and is defined as that dose which decreased the dry weight by 25 or more in 50% of the animals tested. The ED for the test compound was found to be 13.06 mg./kg.

EXAMPLE 4 The analgesic activity of 3-trifluoromethy1-5,6-dihydros-triazolo-[3,4-a1-isoquinoline was determined by the following procedures.

A. Pressure-Pain Method Intraplantar injection of brewers yeast in the hind paw of rats causes an inflammation which increases the sensitivity to pain. This increased sensitivity is susceptible to modification by known analgesic agents. The procedure used is based upon the method described by Randall et al., Arch. Int. Pharmacodyn. 111: 498 (1957). Rats were injected in the left hind paw with 0.1 ml. of a 20% brewers yeast suspension. One hour later the test compound was administered orally via stomach tube. The pain threshold was measured an hour after administration of the'compound by applying a steadily increasing pressure of 16 grams/ second to the inflamed paw. The end point (pain threshold) was defined as the pressure necessary to cause the animal to struggle and/or vocalize.

The effective analgesic dose was obtained by determining the amount of test compound required to cause a 50% increase in the mean pain threshold over that of parallel groups of control animals. For 3-trifluoromethyl- 5,6-dihydro-s-triazolo-[3,4-a]-isoquinoline, the analgesic dose was found to be mg./kg.

B. Anti-Writhing Intraperitoneal injection of 0.2 ml. of 0.02% phenyl-pquinone (P.P.Q.) in mice causes an acute abdominal pain which is characterized by numerous writhing episodes (contraction and torsion of the abdomen). The method.

of controls. The ED for 3-trifluoromethyl-5,6-dihydro-striazolo-[3,4-a]-isoquino1ine was found to be 55 mg./kg.

EXAMPLE 5 The anti-secretory properties of 3-trifiuoromethyl-5,6- dihydro-s-triazolo-[3,4-a]-isoquinoline was determined using the following procedure. The stomachs of fasting rats were ligated at the pylorus (Shay rat procedure) immediately followed by intraperitoneal injection of the test compound. Four hours later the animals were sacrificed, the stomachs removed and the total volume of fluid was measured. The ED for 3-trifluoromethyl-5,6-dihydro-striazolo-[3,4-a] -isoquinoline was found to be 105 mg./kg. (i.e., there was a 50% decrease in gastric secretion at a dosage level of 105 mg./kg.).

EXAMPLE 6 Determination of acute (48 hour) and delayed (5 day) lethality after single doses in mice with 3-trifiuoromethyl- 5,6-dihydro-s-triazolo-[3,4-a1-isoquinoline gave the following data for the 50% lethal dose (LD Mice (Intraperitoneal injection) LD =405 mg./kg.-48 hours LD =389 mg./kg.5 days Mice (oral) LD =1136.7 mg./kg.48 hours LD =1136.7 mg./kg.-5 days In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As various changes could be made in the above methods and compositions without departing from the scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A method of reducing inflammation in a mammal having such a disorder which comprises administering 3- trifluoromethyl-S,6-dihydro s triazolo-[3,4-a]-isoquinoline to said mammal in an amount sufficient to exert an anti-inflammatory effect.

References Cited UNITED STATES PATENTS 3,354,164 11/1967 Francis 260288 3,639,406 2/1972 Reimlinger 260288 FOREIGN PATENTS 1,573,135 7/1969 France 260-288 STANLEY J. FRIEDMAN, Assistant Examiner US. Cl. X.R. 260288 

